Children with motor-speech disorders who use augmentative and alternative communication (AAC) are reported to experience a wide range of vocabulary and grammatical difficulties. Poor vocabulary and grammatical skills profoundly impact an individual's life in a number of ways, including academically, socially and vocationally. This study is driven by the need for additional research on intervention methods for vocabulary and grammatical development in children with severe motor-speech disorders who use AAC. Our long-term goal is to better understand the contexts and mechanisms that support vocabulary and grammatical acquisition for children who use AAC due to severe communication impairments. The specific objective of this application is to determine whether participation in conversations about personal experiences results in sustained and generalized vocabulary growth and improved grammatical skills in children with severe motor- speech disorders who use AAC. Our central hypothesis is that intervention focused on participation in conversations about personal experiences will significantly increase the expressive vocabulary and grammatical skills in this population and that these gains will be sustained and generalized. The rationale underlying this research is that understanding the contexts and mechanisms which support vocabulary and grammatical development in this population has the potential to translate into better clinical treatments for an estimated 5% of all school-age children in the US who receive Special Education services. Our hypothesis will be tested by pursuing two specific aims: 1) to determine the effects of a conversation-based intervention on vocabulary acquisition and 2) on the grammatical skills of children with motor-speech disorders who use AAC. The study will use an experimental repeated measures single-subject design to measure the expressive vocabulary and grammatical skills of 18 school-age children with motor-speech disorders who use AAC before, during and after participation in a conversation-based intervention. Our approach, which is solidly grounded in current theories of vocabulary and grammatical development, is innovative because it will test these theories using a novel combination of measures to assess the vocabulary and grammatical skills of participants over time, and because it utilizes naturally occurring conversations with adults blinded to the intervention procedures to test for generalization of learned skills. The proposed research is significant because it is expected to provide validated clinical strategies to support the expressive vocabulary and grammatical skills acquisition of school-age children with severe motor-speech disorders who use AAC. Accomplishing our objectives with the help of undergraduate and graduate students of communication disorders is consistent with AREA program objectives as it will expose students to meritorious research, will promote the importance of research as a foundation for clinical practice, and will build research infrastructur at an urban comprehensive public university. PUBLIC HEALTH RELEVANCE: The proposed research will inform the development of clinical strategies to protect and improve the health of children with severe communication disorders and, as well, will contribute fundamental knowledge to reduce the burdens of human disability. It will also train undergraduate and graduate students in the importance of research as a foundation for clinical practice.